Someone I know got screwed over when 3G shut down. Their business used an alarm system with a 3G modem (using a cheap data-only SIM card).
The "updated" version requires subscriptions, an app, and goes through manufacturer's servers, so more expensive, and several more points of failure.
As a software developer, this has got to be one of the most original unintended usage scenarios / reasons.
No amount of planning or testing in software will prepare you for ways users will actually use it.